An internal architecture of a network device is that a front board module is disposed in the front, a rear board module orthogonal to the front board module is disposed in the rear, and a backplane is disposed between the front and rear board modules. Signal transmission is implemented by using the backplane. The front board module is placed vertically, the rear board module is placed horizontally, and the backplane is disposed between the front board module and the rear board module. A rear end of the network device further includes a fan, to dissipate heat for the front and rear board modules. Because a heat dissipation air duct of the front board module is blocked by the backplane, air flows to a periphery of the backplane, bypasses the backplane, and is finally sucked out of the network device by the fan after passing through the rear board module.
This heat dissipation architecture has the following disadvantages: a backplane between front and rear board modules blocks ventilation between the front and the rear board modules. As a result, the network device has complex air ducts and many turns, and heat dissipation effect is poor, which is especially not beneficial to heat dissipation of the rear board module. Because air for dissipating heat from the rear board module first passes through the front board module, cascading heating exists, that is, heat from the front board module is brought to an area of the rear board module. Therefore, the rear board module works in a high temperature environment for a long time, and is easily damaged, and a service life is reduced.